I use Prismacolor Artist grade colored pencils. I use them in conjunction with the acrylics, as I work in layers. In order to make the surface accept colored pencil, I coat the area where I want to work with Liquitex matte medium, then coat the pencil areas with additional washes of transparent acrylic or plain gloss or matte medium. And work back and forth like that…….paint, pencil, paint, pencil. Mostly the pencil is used just for definition and subtle color changes…..never big thick areas of it.